RESEARCH ARTICLE Mass spectrometry identification of granins and other proteins secreted by neuroblastoma cells

Abstract We used mass spectrometry-based protein identi-fication to determine the presence of granins and other pro-teins in the mouse neuroblastoma secretome. We detected polypeptides derived from four members of the granin fam-ily: chromogranin A, chromogranin B, secretogranin III, and VGF. Many of them are derived from previously described biologically active regions; however, for VGF and CgB, we detected peptides not related to known bioactivities. Along with granins, we identified 115 other proteins secreted by mouse neuroblastoma cells, belonging to different function-al categories. Fifty-six out of 119 detected proteins possess the signal fragments required for translocation into endo-plasmic reticulum. Sequences of remaining 63 proteins were analyzed using SecretomeP algorithm to determine proba-bility of nonclassical secretion. Identified proteins are in-volved in the regulation of cell cycle, proliferation, apoptosis, angiogenesis, proteolysis, and cell adhesion